[c-nsp] Output Drops

[Rodney Dunn]

If it's congestion Peder the drops should show up in the service-policy
output. Something doesn't look right. What code is it?

Every drop in the service poicy will overload to the output drop in
'sh int' but it's not always 100% true the other way around. I don't
know all the places where that happens though.

I'd try a couple things:

a) remove the service-policy and see if the drops stop
b) remove the service-policy and put a policer on there to
   conform and transmit and exceed and transmit to see if you
   are bursting to the linerate

I wonder if it's a bug in the dQOS code where we are not reporting
the drops just right or something.

Rodney



On Wed, Feb 15, 2006 at 09:58:13AM -0600, Peder @ NetworkOblivion wrote:
> I've got a problem with output drops and I can't quite figure out what 
> the issue is.  I am running 12.2.29 on a 7505.  Here is the config for 
> the relevant interface:
> 
> interface Serial1/0/0:13
>   ip address x.x.x.1 255.255.255.252
>   service-policy output CUSTOMER-MAP
>   encapsulation ppp
> 
> class-map match-all CUSTOMER
>    match access-group name ToCustomer
>    match ip precedence 5
> 
> policy-map CUSTOMER-MAP
>    class CUSTOMER
>      priority 512
>    class class-default
>      fair-queue
> 
> Basically, we are matching IP Prec 5 and a specific IP on the 
> access-list for priority of voice.  The customer is complaining about 
> quality issues every now and then.  When I check the inteface, I am 
> seeing output drops even though there is a small amount of traffic.  The 
> output below shows 40 packets dropped in 7 minutes.  I have a graph of 
> utilization that updates every 30 seconds and it is never above 500kbps. 
>   The 5-min average is ~115,000 bps.
> 
> 
> 7505#sh int Serial1/0/0:13
> Serial1/0/0:13 is up, line protocol is up
>    Hardware is cyBus T3
>    Description: Blah
>    Internet address is x.x.x.1/30
>    MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
>       reliability 255/255, txload 18/255, rxload 7/255
>    Encapsulation PPP, crc 16, loopback not set
>    Keepalive set (10 sec)
>    LCP Open
>    Listen: CDPCP
>    Open: IPCP
>    Last input 00:00:00, output 00:00:01, output hang never
>    Last clearing of "show interface" counters 00:07:03
>    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 40
>    Queueing strategy: VIP-based fair queuing
>    Output queue: 0/40 (size/max)
>    5 minute input rate 43000 bits/sec, 58 packets/sec
>    5 minute output rate 114000 bits/sec, 62 packets/sec
>       27965 packets input, 3012703 bytes, 0 no buffer
>       Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>       0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
>       29856 packets output, 9627702 bytes, 0 underruns
>       0 output errors, 0 collisions, 0 interface resets
>       0 output buffer failures, 0 output buffers swapped out
>       0 carrier transitions no alarm present
>    Timeslot(s) Used: 1-24, Transmitter delay is 0 flags
>    non-inverted data
> 
> 
> 7505#sh pol int Serial1/0/0:13
>   Serial1/0/0:13
> 
>    Service-policy output: CUSTOMER-MAP
> 
>      queue stats for all priority classes:
>        queue size 0, queue limit 128
>        packets output 34124, packet drops 0
>        tail/random drops 0, no buffer drops 0, other drops 0
> 
>      Class-map: CUSTOMER (match-all)
>        34124 packets, 2183936 bytes
>        5 minute offered rate 48000 bps, drop rate 0 bps
>        Match: access-group name ToCustomer
>        Match: ip precedence 5
>        Priority: kbps 512, burst bytes 12800, b/w exceed drops: 0
> 
>      Class-map: class-default (match-any)
>        11127 packets, 10132207 bytes
>        5 minute offered rate 88000 bps, drop rate 0 bps
>        Match: any
>        queue size 0, queue limit 256
>        packets output 11171, packet drops 0
>        tail/random drops 0, no buffer drops 0, other drops 0
>        Fair-queue: per-flow queue limit 64
> 
> The policy doesn't show any drops due to bandwidth and the interface 
> isn't going down, so what is causing the drops?  Is there some other 
> commands I can use to try and figure that out?  Or does this sound like 
> a bug?  We've been running this version for ~ 40 weeks and they just 
> started complaining in the last 2-3 weeks.
> 
> Thanks.
> 
> Peder
> 
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